Often following a neurological injury one or both of the upper extremities are affected with hemiparsis. Hemiparsis is a condition wherein the arm and hand no longer function as they should, and the patient is unable to use or has decreased use of the affected arm and hand. If this condition is not addressed at the onset with a positioning splint, the fingers usually rest in a curled or fisted position. The curled position leads to soft tissue shortening of the long finger flexors (FDS & FDP). Soft tissue shortening often results in contracture of these muscles, which leads to decreased range of motion at the wrist and finger joints. Specifically, a contracture is a shortening of a muscle or tendon in the body in response to stress exerted on that muscle or tendon. As the soft tissue shortening begins and when the patient becomes more active, two other conditions may occur, hypertonicity and spasticity. These conditions will usually pull a person's fingers into a closed first thereby further increasing soft tissue shortening.
Many current splint designs position the user's wrist and hand in varying degrees of flexion with the goal being extension. This positioning is used in order to help prevent or correct muscle contracture. In the case of a chronic hand, splints can usually be positioned to accommodate the hand's current length depending on soft tissue shortening, and gradually be adjusted in varying degrees of extension to help provide a low load, long duration stretch to the long finger flexors.
Many current splint designs have a combined forearm and hand section and are either volar or dorsal based. Sometimes they will be dorsal based at the forearm and volar based at the hand. Other designs offer a forearm section and a separate hand piece. These designs are joined together at the wrist with one or two outriggers or struts, typically with a hinge mechanism on one or both sides of the wrist. These hinges are either static progressive or dynamic in nature. The struts that connect the forearm and hand piece via the wrist hinge are usually on both the ulnar and radial sides, however there may be only one on one side. The static progressive hinge component can be adjusted over time, in varying degrees of flexion/extension, and does not offer a continuous force in extension. This allows the health care professional to start at the patient's current position and move in incremental units towards extension as the soft tissue stretches.
Some splint models offer a dynamic hinge that can be adjusted to put a desired amount of continuous tension toward extension to help facilitate the wrist and fingers in an extended position with a low load, long duration stretch.
Improvements to available designs are needed with regard to the static hand piece. More particularly, as a dynamic neurologically-impaired hand is affected with hypertonicity and spasticity, a patient's fingers tend to want to move into a flexed or fisted position. However, the splint forces the hand to stay in an outstretched position thereby causing the hand to continue to move into flexion against the static hand piece. Often the joints in the fingers of the hand are damaged or deformed because the hand continues to contract against the rigid splint. Thus, joint deformities of the fingers are a common problem when splinting the dynamic neurologically-impaired hand, using a static hand piece.
A dynamic splint that may address one or more of these concerns is disclosed in International Patent Application No. PCT/US2005/047600 which published on Jul. 6, 2006 as WO/2006/072068; and in U.S. Patent Application Publication No. 2007/0055191 which published on Mar. 8, 2007, both of which are incorporated herein by reference. The splint assembly of the present invention represents new variations in the embodiments of the splints disclosed in these two patent references.